Wade Zimmerman addressed this in a previous thread:
"In the finder find the type of file you have link, that is tiff or jpeg or psd or png, file type . When you find one g control or right click on the icon and from the contextual menu choose get info. You will see in the get info dialog a category Open with if it is not expanded expand it and change the application from Preview to Photoshop and then below tht you will see something like apply to all of this type. Click that as well."
So you are essentially go to the file itself and changing the default program with which it opens. So, instead of changing the default from Preview to Photoshop, it would be from Paint to Photoshop.
I hope this works for you!